VR3 BUH or VPM

Inspired Trainer · 13th April 2008, 21:24

Quote: (Originally Posted by rossh)

The V-Planner Live firmware operation has been tested to 650m, and to 30 hours of dive time.

Sounds very Abyss circa 1999 marketing spin Ross, TESTED HOW? on your PC? This testing is worth what exactly? I've added a pic of some similar fairy-land claims below. Wasnt there another version called Commercial apparently 'tested' to 600m!

I used X1 V-Planner Live recently for 60mins at 20metres at 1.1 setpoint (+3)compared with VR3 at 20% conserv and 1.1 setpoint. VR3 gave 11mins TTS at end of bottom time and X1 gave 6mins NDL remaining...then i notice that X1 setpoint is still at 0.70 throughout dive ! now that was scary - if i had of followed it maybe i would have been bent by user error again

or a nadgers more likely is that the deco was woefully inadequate?

will there be a X1/B and then a X1/B/E and then a X1 buhlmann? check ebay for the one i borrowed until then

Bends getting less is total BS...what planet are you on? there were 5 just yesterday in sharm I heard from the jungle drums (tech cave)

touch paper lit...standing down wind

rossh · 14th April 2008, 02:24

Quote: (Originally Posted by Inspired Trainer)

I used X1 V-Planner Live recently for 60mins at 20metres at 1.1 setpoint (+3)compared with VR3 at 20% conserv and 1.1 setpoint. VR3 gave 11mins TTS at end of bottom time and X1 gave 6mins NDL remaining...then i notice that X1 setpoint is still at 0.70 throughout dive ! now that was scary - if i had of followed it maybe i would have been bent by user error again

or a nadgers more likely is that the deco was woefully inadequate?

.
.
Thank you for your field test Mark. Lets look a bit closer at the numbers... We will check these against a recreational PADI NDL. 60 mins, assume an average bottom depth through out of 18m, assuming air dil and convert depths to EAD for direct comparisons. As shown below, V-Planner Live was correct all along.

****

On the V-Planner Live, 0.7 setpoint = an equivalent inspired mix of EAN 23%, unit indicated 6 mins NDL after 1 hour.

EAD = (0.77 / 0.79) x (18m + 10) - 10
EAD = 17.29m

Using PADI RDP wheel - 17m / 55ft == NDL 65 minutes
Therefore, 60 mins run time == 5mins NDL shown. This confirms correct operation of V-Planner Live.

****

On the VR3 numbers. setpoint 1.1 = inspired equivalent mix of EAN37%, unit indicated 11 mins deco after 1 hour.

EAD = (0.63 / 0.79) x (18m + 10) - 10
EAD = 12.32m

PADI RDP wheel 12m / 39ft == NDL of 123 minutes.
Big error. NDL is 123 mins, but VR3 required 11 mins of deco after just 1 hour (half way to real NDL).

****

So... V-Planner Live was exactly right, and within a minute or two of established NDL's. VR3 was in error by over 1 hour. Maybe you should sell your VR3 instead Mark?
.

Gasman · 14th April 2008, 06:18

Quote:

DCS treatment numbers... Andrew, How many treatments have you done on Haldane, Bulhmann patients - 500, 1000, more?

25% ... sounds like FUD Andrew.

FUD? 12 divers dive a wreck at 75 msw on 3 different occasions (4 divers per team) all using the same deco model and the same runtimes / bottoms time. All experienced. Each time one diver in the group gets bent. 2 needed to be air lifted with spinal symptoms..... 3 out of 12 = 25% last time I looked! Next event, 3 divers diving 125m, one diver bent, severe MS symptoms .... 33%?
shall I go on?

Sure I've treated lots of cases on Buhlmann.... I never said I hadn't. However, what we are seeing here is a very high rate of DCI with a particular model that is meant to reduce bubbling and clearly isn't. Maybe these people would have got bent using Buhlmann.... ... maybe they wouldn't have. What I do know is that when we have used our ultrasound to look at bubbling levels in dives over 60m we are seeing very high grade bubbling occuring in divers using the "bubble" models.

You will notice, that I clearly stated in the previous post that the studies that were done did not use the models usually used by technical divers. However, the point is, that adding time deep without adequately compensating by adding time shallow does not seem to reduce the decompression stress as some bubble models would predict it should.

I am not getting into a slanging match saying "X" algorithm is better than "Y". What I am trying to give the members of this forum is information on the current best scientific information we have. What they do with it and how they interpret it is their bussiness.

Andrew

1. Blatteau JE, Hugon M, Gardette B, Galland FM, editors. Decompression profiles with deep stops: Comparative doppler study with procedures of the French Navy. EUBS, Proceedings of the 30th Annual Scientific meeting of the European Underwater Baromedical Society; 2004 Sept 2004; Ajaccio, Corsica, France. EUBS.
2. Gerth WA, Gault KA, Doolette DJ. Empirical Evaluation of the efficacy of deep stops in air decompression dives. UHMS; 2007 June 2007
Hawaii. 2007.
3. Brubakk AO, Gutvik C, editors. Optimal Decompression from 90 msw. Proceedings of the Advanced Scientific Diving Workshop; 2006 February 23-24 2006; Smithsonian Institution Washington DC. Smithsonian Institution.

silent running · 14th April 2008, 07:34

Quote: (Originally Posted by Gasman)

FUD? 12 divers dive a wreck at 75 msw on 3 different occasions (4 divers per team) all using the same deco model and the same runtimes / bottoms time. All experienced. Each time one diver in the group gets bent. 2 needed to be air lifted with spinal symptoms..... 3 out of 12 = 25% last time I looked! Next event, 3 divers diving 125m, one diver bent, severe MS symptoms .... 33%?
shall I go on?

Sure I've treated lots of cases on Buhlmann.... I never said I hadn't. However, what we are seeing here is a very high rate of DCI with a particular model that is meant to reduce bubbling and clearly isn't. Maybe these people would have got bent using Buhlmann.... ... maybe they wouldn't have. What I do know is that when we have used our ultrasound to look at bubbling levels in dives over 60m we are seeing very high grade bubbling occuring in divers using the "bubble" models.

You will notice, that I clearly stated in the previous post that the studies that were done did not use the models usually used by technical divers. However, the point is, that adding time deep without adequately compensating by adding time shallow does not seem to reduce the decompression stress as some bubble models would predict it should.

I am not getting into a slanging match saying "X" algorithm is better than "Y". What I am trying to give the members of this forum is information on the current best scientific information we have. What they do with it and how they interpret it is their bussiness.

Andrew

1. Blatteau JE, Hugon M, Gardette B, Galland FM, editors. Decompression profiles with deep stops: Comparative doppler study with procedures of the French Navy. EUBS, Proceedings of the 30th Annual Scientific meeting of the European Underwater Baromedical Society; 2004 Sept 2004; Ajaccio, Corsica, France. EUBS.
2. Gerth WA, Gault KA, Doolette DJ. Empirical Evaluation of the efficacy of deep stops in air decompression dives. UHMS; 2007 June 2007
Hawaii. 2007.
3. Brubakk AO, Gutvik C, editors. Optimal Decompression from 90 msw. Proceedings of the Advanced Scientific Diving Workshop; 2006 February 23-24 2006; Smithsonian Institution Washington DC. Smithsonian Institution.

OK Gasman, thanks for all the info. I have no reason to doubt what you have posted thus far and thanks for bothering to do so.

I am a new tmix diver who was taught tmix along with RGBM and whether we are talking about VPM or RGBM bubble models, the principle of trying to minimize/control bubble growth with deep stops seems sound enough to me especially given the anecdotal experience of commercial pearl divers from Okinawa and Hawaii doing repet dives beyond 300ft on a daily basis. And given the lack of significant numbers of technical HE dives and the necessary corresponding control groups for buhlman or any other alg, why shouldn't I go with the alg that makes the most sense to me?

The literature I have from my course states that to date, there have been 1000's of manned dives and animal test dives on RGBM with single digit incidents of dcs. By extrapolation, I could say that no matter where we put the deep stops, using that pressure to reduce/minimize bubble growth as opposed to bend and mend in the shallows ala buhlman, is less injurious to the body and a more healthy approach. That is my assumption and unless anyone can produce a study that proves we are better off using a maximum pressure gradient to squeeze out inert gas in the shallows as opposed to some kind of deep stops, I will continue to try and refine this practice.

In other words, the question for those of us who believe this is the right approach isn't whether we will do deep stops, it's how deep will we start them and how long. I distinctly remember my USN trained tmix instructor telling me before a 30 minute high workload dive moving logs off a wreck at 70 meters that all the 1 minute deep stops weren't as important to follow to the second as a VERY slow ascent rate. In otherwords, it was all about a SLOW ascent rate to get rid of the fast-he-inert gas without getting bent.

For my own purposes, I prefer to follow my RGBM alg in my HE computer AND spend the additional time at 9-6 meters with my buhlman VR3 buddies. That seems the most prudent approach to me given the lack of solid data to support either deep stops or a bend and mend approach, especially given this discussion of the topic on this thread.

Sorry to be wordy, I'm just a babe in the woods, but your and anyone else's thoughts on this subject would be most appreciated as I'm sure I could be missing something...

Thanks, -Andy

Mark Chase · 14th April 2008, 07:52

Quote: (Originally Posted by Drmike)

yup

Doesnt the algo penalise you for He? In which case doesnt switching comp to air infact give you less conservation?

Personaly when we are less certain about something I lean to side of caution rather than other way around, and I really dont see theres that much hurry to get out the water (cave, OW with good conditions)

I havent ever dived with anyone (or heard of anyone) doing air deco off mix on big dives. I assume theres a big effect on deco time. Theres no way Ive got big enough balls to do that without more validation first. Risk V reward is nowhere near good enough for me to try that.

Unless Im in really truly terrible currents and swell in the middle of a shipping lane (so no floating platform) shaving off half hour here or hour there is really not worth it in my opinion if you consider what your risking. A lot of my dives are long 6-10hrs range so in relation taking risk just to save an hour or so is just not something Im comfortable with - id rather just sit there a few hours longer and know with higher level of certainty that im gonna be able to sustain an erection after the dive

Ive dived with a few guys who were always hunting for quick deco. Both of them still dive and dive deep, but both of them have permanent neurodamage sustained on dives we did together where I did signif longer deco than them. That may be a coincidence but it is something I consider when the urge to cut deco time starts to be so strong

Kevin Gurr

ATB

Mark Chase

Mark Chase · 14th April 2008, 07:56

Quote: (Originally Posted by Gasman)

Hi all,

Without getting into to the emotive replies that this topic always creates, here are the facts as we presently understand them.

There have been 3 studies so far conducted specifically looking at deep stops in the technical diving range. 2 are human, (a French Navy study and a USN study) and an animal study from Alf Brubakk’s group in Norway. None of these studies has specifically looked at VPM. However, they have compared dive profiles where the total dive time is the same in each profile but one profile has deep stops and the other doesn’t.

The results:

The French navy study showed higher ultrasound bubble rates in the deep stop group and where a repetitive dive was conducted, there was a higher DCI rate in the deep stop group.

The USN had to stop the study early because the divers in the deep stop group were getting spinal cord DCI at a rather alarming rate.

The Animal study was stopped early because the pigs in the deep stop group died.

While more studies need to be done, it would appear from the presently available data that deep stops are not living up to their promise. This is not totally unexpected as, if one trawls the literature, there were attempts to use deep stops to produce decompression profiles for deep (500 ft) dives in the 1980’s. It didn’t work too well then either, with many of the test divers getting bent and a considerable “tweaking” of the algorithm needed to get it to work…… and in the end the TDT was much greater than the “traditional” algorithm which also worked.

We have seen a fairly high DCI rate in people using a bubble model for deep dives (up to 25%) including two recent cases of spinal cord DCI. In addition we recently ultrasounded divers after 75m dives of 30-40 BT (CCR, Trimix diluent) and observed grade 4+ bubbling in those using the deep stop / bubble algorithm. I had never seen bubbling of this level before outside of a lab during echo contrast studies.

Before anyone asks I will not comment on specific algorithms on this forum. Take the above information and make your own decisions.

Andrew

Any Internet links available for these studies?

You see this is the problem. All i am trying to do is stay safe.

When I started doing deco dives (2000) I used Buhlman tables. I read what i could and learned about Pyle stops and implemented them. Then In 2002 I got Decoplanner and started cutting GF 30/90 tables. Following the accepted norm at that time i was gas switching from back gas 18/45 or 14/60 straight on to 32% nitrox at 40m.

No problems at all so far but i am new so the dives are not big less than 90mins deco.

I dream of a VR3 because I hate the restrictions of tables and in 03 I finally get one. The deep stops seem very deep and the jumps to the shallow stops seems relay big. Its also very conservative so i am running it on zero.

Still no problems still switching to Nitrox from back gas.

Then DOTF (Ratio deco) comes to my attention. We are apparently all doing it wrong and we should be stopping at 80% ATA's and doing half the shallow stops Buhlman reckons because we used to think Helium is bad but actually its gods gift to deco divers.

So now we are lyeing to the VR3 telling it we are using half the helium we are actually using. Faster deco is the result.

Dr JM bends himself playing this game and i decide its just daft so I stop.

By now I am running 150-180mins of deco and so far so good.

By 2005 I have a handle on DOTF and I am starting to implement a 3m/min ascent rate from the VR3s deep stop. Its fine but its loading the shallow stop time. From 21m and up i am adding stops every three m. This is in vogue at the moment but i am still doing the long shallow stops where as the DOTF boys are telling me its a waste of my life. About now VPM-B shows up in my life and seems to back up what the DIR boys are saying.

I get hold of a copy and dream about the VPMB upgrade for the VR3 which was a twinkle in Kevin's eye at that time.

VPM-B level 2 seemed the norm and it scares me with its short shallow stops. The deep stops don't seem much different from the 20/80GFs i am running but switch to 10/90 to try and mimic the profiles a little closer.

2005 i am now doing deco dives on my CCR and following the latest trends I am running helium in the mix all the way out.

I am running one VR3s on a 1.25 set point and the other is plumbed in to a cell zero safety.

I get sub clinical bent twice on nothing 40m dives. So does my buddy.

Switch to pure 02 CCR at 6m for the last 20mins of deco (still with VR3 plumbed in running zero) and all is well again.

VPM VR3 is launched but the upgrade cost prevents me being first in the cue (£1000 for my two VR3s)

Sounds like i had a lucky break because the complaints about the VPM VR3 start rolling in.

2006 Buy a Hammer head with GF deco and it seems all my prayers are answered. The deco profiles don't need fudging to get the curve i want and i can go easily from conservative to aggressive and all shades in between.

10/90GF and 02 for 20mins at 6m and no problems to report so far.

2006/7 Bought a Shearwater GF unit plumbed in to my new KISS 10/90GF seems fine.

2008. Starting to hear roomers that deep stops are in fact bad for you. I never believed they shortened shallow deco the way the DIR boys said and have argued against it avidly but now it seems even Dr Doolittle is speaking at the GUE conference and saying the same thing.

2007/2008 growing bad press about VPM-B. Roomers of high rates of DCI and deep divers abandoning VPM as a planning option.

2009? god knows perhaps every body's back on BSAC88's ?

ATB

Mark

a

ATB

Mark

rossh · 14th April 2008, 08:31

Quote: (Originally Posted by Gasman)

FUD? 12 divers dive a wreck at 75 msw on 3 different occasions (4 divers per team) all using the same deco model and the same runtimes / bottoms time. All experienced. Each time one diver in the group gets bent. 2 needed to be air lifted with spinal symptoms..... 3 out of 12 = 25% last time I looked! Next event, 3 divers diving 125m, one diver bent, severe MS symptoms .... 33%?
shall I go on?

.
You should, but more importantly, take a close look at the procedures and diving practices used in each, and tell us what went wrong with these?

75m is a very common dive. Hundreds of divers go to this depth every weekend for fun, in all sorts of places the world over. Most use a plan with some form of deep stop system, many use a bubble model, and they all seem to return just fine. Your implied suggestion that deep stops and bubble models are at fault, just does not add up. The real world dive practices used today simply do not agree with you Andrew.

3 divers to 125m - two are OK, so what did diver 3 do wrong? And severe MS symptoms too? This suggests that the injured diver has other problems to resolve, and a few extra minutes of deco was not going to help the situation.

So Andrew, please get off this "the model did it too me" nonsense, and kindly start looking at the real underlying cause of each set of problems.

In the past decade, the whole tech / rec industry has moved away from traditional "man tested" models. I wish some in the medical community would catch up to this new reality. This concept of staying to approved systems sounds nice, but the reality is almost no divers wants to use these anyway. Divers have been fine tuning their diving practices for better results, and now its up to the medical community to discover why.

The recent Navy test has nothing to do with tech practices in use today. Bubble soundings are not much use either. I'll give credit to the work of Alf Brubakk, but I'm not sure it provides much detail either way.

*************

Gasman · 14th April 2008, 08:36

Hi Mark,

One of the Brubakk papers (which is not actually the study I quoted, as that is presently only as an abstract after presentation at EUBS) is available online at
Smithsonian Scientific Diving Program - Science diving information and authorization forms

Advanced Scientific Diving Workshop
Lang, M.A. & Smith, N.E. (ed) 2006. Proceedings of the Advanced Scientific Diving Workshop. Smithsonian Institution, Washington D.C., 277p.

This workshop proceedings has some very informative papers on decompression from some of the leaders in the field including JP Imbert (ex COMEX).

The other papers are not easily accessible on line at present. Wayne Gerth presented the USN study at the recent DAN tech diving workshop.

Andrew

Inspired Trainer · 14th April 2008, 10:15

Ross,

if i could have made a bet last night about your response then i would now be slightly richer

of course the dive was not to 20m - that was the average depth. I hope you realise that when programming v-planner live that average depth is useful for calculating approx gas use but no use when making deco calcs? ive got this awful feeling that this is the mistake youve made in the X1 much like your vpm boyles law 'oversight'

Silent Running, i appreciate you state you are new to this, but you have largely reprinted wienkes spiel about rgbm validation from his website. 1000's of suunto ghekko no-deco dives hardly validate it as a deco model...would you agree? The only 'full' rgbm deco computer should be avoided like the plague, many have been bent with it.

FYI suunto only use rgbm on their cardboard boxes - not in their metal ones!

How come the peddlers of rgbm/vpm use no-deco dives or tech bimbles to validate/augment their work but when actually used to 'everyday' depths as you say Ross, the divers get bent and you simply blame pilot error? What are we doing wrong oh guru?

Mark

***diverklondike*** · 14th April 2008, 10:39

Quote: (Originally Posted by Inspired Trainer)

Ross,

if i could have made a bet last night about your response then i would now be slightly richer

of course the dive was not to 20m - that was the average depth. I hope you realise that when programming v-planner live that average depth is useful for calculating approx gas use but no use when making deco calcs? ive got this awful feeling that this is the mistake youve made in the X1 much like your vpm boyles law 'oversight'

Silent Running, i appreciate you state you are new to this, but you have largely reprinted wienkes spiel about rgbm validation from his website. 1000's of suunto ghekko no-deco dives hardly validate it as a deco model...would you agree? The only 'full' rgbm deco computer should be avoided like the plague, many have been bent with it.

FYI suunto only use rgbm on their cardboard boxes - not in their metal ones!

How come the peddlers of rgbm/vpm use no-deco dives or tech bimbles to validate/augment their work but when actually used to 'everyday' depths as you say Ross, the divers get bent and you simply blame pilot error? What are we doing wrong oh guru?

Mark

Mark,

This this point you seem to be pretty focused on baiting other people. In your previous post, you specifically say "20M" and now you change your story...

************************************************** *******
I used X1 V-Planner Live recently for 60mins at 20metres at 1.1 setpoint (+3)compared with VR3 at 20% conserv and 1.1 setpoint. ************************************************** *****

How about contrubuting something versus just bashing everyone...

Thanks

Mark

14th April 2008, 02:24	#102 (permalink)
rossh Custom Title Allowed! Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Jul 2005 Location: Canada Posts: 106	Re: VR3 BUH or VPM Quote: (Originally Posted by Inspired Trainer) I used X1 V-Planner Live recently for 60mins at 20metres at 1.1 setpoint (+3)compared with VR3 at 20% conserv and 1.1 setpoint. VR3 gave 11mins TTS at end of bottom time and X1 gave 6mins NDL remaining...then i notice that X1 setpoint is still at 0.70 throughout dive ! now that was scary - if i had of followed it maybe i would have been bent by user error again or a nadgers more likely is that the deco was woefully inadequate? . . Thank you for your field test Mark. Lets look a bit closer at the numbers... We will check these against a recreational PADI NDL. 60 mins, assume an average bottom depth through out of 18m, assuming air dil and convert depths to EAD for direct comparisons. As shown below, V-Planner Live was correct all along. ** On the V-Planner Live, 0.7 setpoint = an equivalent inspired mix of EAN 23%, unit indicated 6 mins NDL after 1 hour. EAD = (0.77 / 0.79) x (18m + 10) - 10 EAD = 17.29m Using PADI RDP wheel - 17m / 55ft == NDL 65 minutes Therefore, 60 mins run time == 5mins NDL shown. This confirms correct operation of V-Planner Live. On the VR3 numbers. setpoint 1.1 = inspired equivalent mix of EAN37%, unit indicated 11 mins deco after 1 hour. EAD = (0.63 / 0.79) x (18m + 10) - 10 EAD = 12.32m PADI RDP wheel 12m / 39ft == NDL of 123 minutes. Big error. NDL is 123 mins, but VR3 required 11 mins of deco after just 1 hour (half way to real NDL). So... V-Planner Live was exactly right, and within a minute or two of established NDL's. VR3 was in error by over 1 hour. Maybe you should sell your VR3 instead Mark? . __________________ Regards, Ross Hemingway V-Planner VPM-B Nitrox Trimix CCR Deco planning for Technical Divers** www.v-planner.com Last edited by rossh : 14th April 2008 at 02:27.
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14th April 2008, 06:18	#103 (permalink)
Gasman New Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Join Date: Jul 2005 Location: Australia Posts: 33	Re: VR3 BUH or VPM Quote: DCS treatment numbers... Andrew, How many treatments have you done on Haldane, Bulhmann patients - 500, 1000, more? 25% ... sounds like FUD Andrew. FUD? 12 divers dive a wreck at 75 msw on 3 different occasions (4 divers per team) all using the same deco model and the same runtimes / bottoms time. All experienced. Each time one diver in the group gets bent. 2 needed to be air lifted with spinal symptoms..... 3 out of 12 = 25% last time I looked! Next event, 3 divers diving 125m, one diver bent, severe MS symptoms .... 33%? shall I go on? Sure I've treated lots of cases on Buhlmann.... I never said I hadn't. However, what we are seeing here is a very high rate of DCI with a particular model that is meant to reduce bubbling and clearly isn't. Maybe these people would have got bent using Buhlmann.... ... maybe they wouldn't have. What I do know is that when we have used our ultrasound to look at bubbling levels in dives over 60m we are seeing very high grade bubbling occuring in divers using the "bubble" models. You will notice, that I clearly stated in the previous post that the studies that were done did not use the models usually used by technical divers. However, the point is, that adding time deep without adequately compensating by adding time shallow does not seem to reduce the decompression stress as some bubble models would predict it should. I am not getting into a slanging match saying "X" algorithm is better than "Y". What I am trying to give the members of this forum is information on the current best scientific information we have. What they do with it and how they interpret it is their bussiness. Andrew 1. Blatteau JE, Hugon M, Gardette B, Galland FM, editors. Decompression profiles with deep stops: Comparative doppler study with procedures of the French Navy. EUBS, Proceedings of the 30th Annual Scientific meeting of the European Underwater Baromedical Society; 2004 Sept 2004; Ajaccio, Corsica, France. EUBS. 2. Gerth WA, Gault KA, Doolette DJ. Empirical Evaluation of the efficacy of deep stops in air decompression dives. UHMS; 2007 June 2007 Hawaii. 2007. 3. Brubakk AO, Gutvik C, editors. Optimal Decompression from 90 msw. Proceedings of the Advanced Scientific Diving Workshop; 2006 February 23-24 2006; Smithsonian Institution Washington DC. Smithsonian Institution.
(Offline)

14th April 2008, 07:34	#104 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,813	Re: VR3 BUH or VPM Quote: (Originally Posted by Gasman) FUD? 12 divers dive a wreck at 75 msw on 3 different occasions (4 divers per team) all using the same deco model and the same runtimes / bottoms time. All experienced. Each time one diver in the group gets bent. 2 needed to be air lifted with spinal symptoms..... 3 out of 12 = 25% last time I looked! Next event, 3 divers diving 125m, one diver bent, severe MS symptoms .... 33%? shall I go on? Sure I've treated lots of cases on Buhlmann.... I never said I hadn't. However, what we are seeing here is a very high rate of DCI with a particular model that is meant to reduce bubbling and clearly isn't. Maybe these people would have got bent using Buhlmann.... ... maybe they wouldn't have. What I do know is that when we have used our ultrasound to look at bubbling levels in dives over 60m we are seeing very high grade bubbling occuring in divers using the "bubble" models. You will notice, that I clearly stated in the previous post that the studies that were done did not use the models usually used by technical divers. However, the point is, that adding time deep without adequately compensating by adding time shallow does not seem to reduce the decompression stress as some bubble models would predict it should. I am not getting into a slanging match saying "X" algorithm is better than "Y". What I am trying to give the members of this forum is information on the current best scientific information we have. What they do with it and how they interpret it is their bussiness. Andrew 1. Blatteau JE, Hugon M, Gardette B, Galland FM, editors. Decompression profiles with deep stops: Comparative doppler study with procedures of the French Navy. EUBS, Proceedings of the 30th Annual Scientific meeting of the European Underwater Baromedical Society; 2004 Sept 2004; Ajaccio, Corsica, France. EUBS. 2. Gerth WA, Gault KA, Doolette DJ. Empirical Evaluation of the efficacy of deep stops in air decompression dives. UHMS; 2007 June 2007 Hawaii. 2007. 3. Brubakk AO, Gutvik C, editors. Optimal Decompression from 90 msw. Proceedings of the Advanced Scientific Diving Workshop; 2006 February 23-24 2006; Smithsonian Institution Washington DC. Smithsonian Institution. OK Gasman, thanks for all the info. I have no reason to doubt what you have posted thus far and thanks for bothering to do so. I am a new tmix diver who was taught tmix along with RGBM and whether we are talking about VPM or RGBM bubble models, the principle of trying to minimize/control bubble growth with deep stops seems sound enough to me especially given the anecdotal experience of commercial pearl divers from Okinawa and Hawaii doing repet dives beyond 300ft on a daily basis. And given the lack of significant numbers of technical HE dives and the necessary corresponding control groups for buhlman or any other alg, why shouldn't I go with the alg that makes the most sense to me? The literature I have from my course states that to date, there have been 1000's of manned dives and animal test dives on RGBM with single digit incidents of dcs. By extrapolation, I could say that no matter where we put the deep stops, using that pressure to reduce/minimize bubble growth as opposed to bend and mend in the shallows ala buhlman, is less injurious to the body and a more healthy approach. That is my assumption and unless anyone can produce a study that proves we are better off using a maximum pressure gradient to squeeze out inert gas in the shallows as opposed to some kind of deep stops, I will continue to try and refine this practice. In other words, the question for those of us who believe this is the right approach isn't whether we will do deep stops, it's how deep will we start them and how long. I distinctly remember my USN trained tmix instructor telling me before a 30 minute high workload dive moving logs off a wreck at 70 meters that all the 1 minute deep stops weren't as important to follow to the second as a VERY slow ascent rate. In otherwords, it was all about a SLOW ascent rate to get rid of the fast-he-inert gas without getting bent. For my own purposes, I prefer to follow my RGBM alg in my HE computer AND spend the additional time at 9-6 meters with my buhlman VR3 buddies. That seems the most prudent approach to me given the lack of solid data to support either deep stops or a bend and mend approach, especially given this discussion of the topic on this thread. Sorry to be wordy, I'm just a babe in the woods, but your and anyone else's thoughts on this subject would be most appreciated as I'm sure I could be missing something... Thanks, -Andy
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14th April 2008, 07:52	#105 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,556	Re: VR3 BUH or VPM Quote: (Originally Posted by Drmike) yup Doesnt the algo penalise you for He? In which case doesnt switching comp to air infact give you less conservation? Personaly when we are less certain about something I lean to side of caution rather than other way around, and I really dont see theres that much hurry to get out the water (cave, OW with good conditions) I havent ever dived with anyone (or heard of anyone) doing air deco off mix on big dives. I assume theres a big effect on deco time. Theres no way Ive got big enough balls to do that without more validation first. Risk V reward is nowhere near good enough for me to try that. Unless Im in really truly terrible currents and swell in the middle of a shipping lane (so no floating platform) shaving off half hour here or hour there is really not worth it in my opinion if you consider what your risking. A lot of my dives are long 6-10hrs range so in relation taking risk just to save an hour or so is just not something Im comfortable with - id rather just sit there a few hours longer and know with higher level of certainty that im gonna be able to sustain an erection after the dive Ive dived with a few guys who were always hunting for quick deco. Both of them still dive and dive deep, but both of them have permanent neurodamage sustained on dives we did together where I did signif longer deco than them. That may be a coincidence but it is something I consider when the urge to cut deco time starts to be so strong Kevin Gurr ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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14th April 2008, 07:56	#106 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,556	Re: VR3 BUH or VPM Quote: (Originally Posted by Gasman) Hi all, Without getting into to the emotive replies that this topic always creates, here are the facts as we presently understand them. There have been 3 studies so far conducted specifically looking at deep stops in the technical diving range. 2 are human, (a French Navy study and a USN study) and an animal study from Alf Brubakk’s group in Norway. None of these studies has specifically looked at VPM. However, they have compared dive profiles where the total dive time is the same in each profile but one profile has deep stops and the other doesn’t. The results: The French navy study showed higher ultrasound bubble rates in the deep stop group and where a repetitive dive was conducted, there was a higher DCI rate in the deep stop group. The USN had to stop the study early because the divers in the deep stop group were getting spinal cord DCI at a rather alarming rate. The Animal study was stopped early because the pigs in the deep stop group died. While more studies need to be done, it would appear from the presently available data that deep stops are not living up to their promise. This is not totally unexpected as, if one trawls the literature, there were attempts to use deep stops to produce decompression profiles for deep (500 ft) dives in the 1980’s. It didn’t work too well then either, with many of the test divers getting bent and a considerable “tweaking” of the algorithm needed to get it to work…… and in the end the TDT was much greater than the “traditional” algorithm which also worked. We have seen a fairly high DCI rate in people using a bubble model for deep dives (up to 25%) including two recent cases of spinal cord DCI. In addition we recently ultrasounded divers after 75m dives of 30-40 BT (CCR, Trimix diluent) and observed grade 4+ bubbling in those using the deep stop / bubble algorithm. I had never seen bubbling of this level before outside of a lab during echo contrast studies. Before anyone asks I will not comment on specific algorithms on this forum. Take the above information and make your own decisions. Andrew Any Internet links available for these studies? You see this is the problem. All i am trying to do is stay safe. When I started doing deco dives (2000) I used Buhlman tables. I read what i could and learned about Pyle stops and implemented them. Then In 2002 I got Decoplanner and started cutting GF 30/90 tables. Following the accepted norm at that time i was gas switching from back gas 18/45 or 14/60 straight on to 32% nitrox at 40m. No problems at all so far but i am new so the dives are not big less than 90mins deco. I dream of a VR3 because I hate the restrictions of tables and in 03 I finally get one. The deep stops seem very deep and the jumps to the shallow stops seems relay big. Its also very conservative so i am running it on zero. Still no problems still switching to Nitrox from back gas. Then DOTF (Ratio deco) comes to my attention. We are apparently all doing it wrong and we should be stopping at 80% ATA's and doing half the shallow stops Buhlman reckons because we used to think Helium is bad but actually its gods gift to deco divers. So now we are lyeing to the VR3 telling it we are using half the helium we are actually using. Faster deco is the result. Dr JM bends himself playing this game and i decide its just daft so I stop. By now I am running 150-180mins of deco and so far so good. By 2005 I have a handle on DOTF and I am starting to implement a 3m/min ascent rate from the VR3s deep stop. Its fine but its loading the shallow stop time. From 21m and up i am adding stops every three m. This is in vogue at the moment but i am still doing the long shallow stops where as the DOTF boys are telling me its a waste of my life. About now VPM-B shows up in my life and seems to back up what the DIR boys are saying. I get hold of a copy and dream about the VPMB upgrade for the VR3 which was a twinkle in Kevin's eye at that time. VPM-B level 2 seemed the norm and it scares me with its short shallow stops. The deep stops don't seem much different from the 20/80GFs i am running but switch to 10/90 to try and mimic the profiles a little closer. 2005 i am now doing deco dives on my CCR and following the latest trends I am running helium in the mix all the way out. I am running one VR3s on a 1.25 set point and the other is plumbed in to a cell zero safety. I get sub clinical bent twice on nothing 40m dives. So does my buddy. Switch to pure 02 CCR at 6m for the last 20mins of deco (still with VR3 plumbed in running zero) and all is well again. VPM VR3 is launched but the upgrade cost prevents me being first in the cue (£1000 for my two VR3s) Sounds like i had a lucky break because the complaints about the VPM VR3 start rolling in. 2006 Buy a Hammer head with GF deco and it seems all my prayers are answered. The deco profiles don't need fudging to get the curve i want and i can go easily from conservative to aggressive and all shades in between. 10/90GF and 02 for 20mins at 6m and no problems to report so far. 2006/7 Bought a Shearwater GF unit plumbed in to my new KISS 10/90GF seems fine. 2008. Starting to hear roomers that deep stops are in fact bad for you. I never believed they shortened shallow deco the way the DIR boys said and have argued against it avidly but now it seems even Dr Doolittle is speaking at the GUE conference and saying the same thing. 2007/2008 growing bad press about VPM-B. Roomers of high rates of DCI and deep divers abandoning VPM as a planning option. 2009? god knows perhaps every body's back on BSAC88's ? ATB Mark a ATB Mark __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System Last edited by Mark Chase : 14th April 2008 at 08:37.
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14th April 2008, 08:31	#107 (permalink)
rossh Custom Title Allowed! Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: Jul 2005 Location: Canada Posts: 106	Re: VR3 BUH or VPM Quote: (Originally Posted by Gasman) FUD? 12 divers dive a wreck at 75 msw on 3 different occasions (4 divers per team) all using the same deco model and the same runtimes / bottoms time. All experienced. Each time one diver in the group gets bent. 2 needed to be air lifted with spinal symptoms..... 3 out of 12 = 25% last time I looked! Next event, 3 divers diving 125m, one diver bent, severe MS symptoms .... 33%? shall I go on? . You should, but more importantly, take a close look at the procedures and diving practices used in each, and tell us what went wrong with these? 75m is a very common dive. Hundreds of divers go to this depth every weekend for fun, in all sorts of places the world over. Most use a plan with some form of deep stop system, many use a bubble model, and they all seem to return just fine. Your implied suggestion that deep stops and bubble models are at fault, just does not add up. The real world dive practices used today simply do not agree with you Andrew. 3 divers to 125m - two are OK, so what did diver 3 do wrong? And severe MS symptoms too? This suggests that the injured diver has other problems to resolve, and a few extra minutes of deco was not going to help the situation. So Andrew, please get off this "the model did it too me" nonsense, and kindly start looking at the real underlying cause of each set of problems. In the past decade, the whole tech / rec industry has moved away from traditional "man tested" models. I wish some in the medical community would catch up to this new reality. This concept of staying to approved systems sounds nice, but the reality is almost no divers wants to use these anyway. Divers have been fine tuning their diving practices for better results, and now its up to the medical community to discover why. The recent Navy test has nothing to do with tech practices in use today. Bubble soundings are not much use either. I'll give credit to the work of Alf Brubakk, but I'm not sure it provides much detail either way. *********** __________________ Regards, Ross Hemingway V-Planner VPM-B Nitrox Trimix CCR Deco planning for Technical Divers** www.v-planner.com
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14th April 2008, 08:36	#108 (permalink)
Gasman New Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Join Date: Jul 2005 Location: Australia Posts: 33	Re: VR3 BUH or VPM Hi Mark, One of the Brubakk papers (which is not actually the study I quoted, as that is presently only as an abstract after presentation at EUBS) is available online at Smithsonian Scientific Diving Program - Science diving information and authorization forms Advanced Scientific Diving Workshop Lang, M.A. & Smith, N.E. (ed) 2006. Proceedings of the Advanced Scientific Diving Workshop. Smithsonian Institution, Washington D.C., 277p. This workshop proceedings has some very informative papers on decompression from some of the leaders in the field including JP Imbert (ex COMEX). The other papers are not easily accessible on line at present. Wayne Gerth presented the USN study at the recent DAN tech diving workshop. Andrew
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14th April 2008, 10:15	#109 (permalink)
Inspired Trainer New Member Current Rebreather/s: Pelagian Other Rebreather/s: Pelagian Join Date: Oct 2007 Location: London Posts: 63	Re: VR3 BUH or VPM Ross, if i could have made a bet last night about your response then i would now be slightly richer of course the dive was not to 20m - that was the average depth. I hope you realise that when programming v-planner live that average depth is useful for calculating approx gas use but no use when making deco calcs? ive got this awful feeling that this is the mistake youve made in the X1 much like your vpm boyles law 'oversight' Silent Running, i appreciate you state you are new to this, but you have largely reprinted wienkes spiel about rgbm validation from his website. 1000's of suunto ghekko no-deco dives hardly validate it as a deco model...would you agree? The only 'full' rgbm deco computer should be avoided like the plague, many have been bent with it. FYI suunto only use rgbm on their cardboard boxes - not in their metal ones! How come the peddlers of rgbm/vpm use no-deco dives or tech bimbles to validate/augment their work but when actually used to 'everyday' depths as you say Ross, the divers get bent and you simply blame pilot error? What are we doing wrong oh guru? Mark Last edited by Inspired Trainer : 14th April 2008 at 10:18.
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14th April 2008, 10:39	#110 (permalink)
*diverklondike* Moderator Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Oct 2005 Location: Delaware, USA Posts: 1,557	Re: VR3 BUH or VPM Quote: (Originally Posted by Inspired Trainer) Ross, if i could have made a bet last night about your response then i would now be slightly richer of course the dive was not to 20m - that was the average depth. I hope you realise that when programming v-planner live that average depth is useful for calculating approx gas use but no use when making deco calcs? ive got this awful feeling that this is the mistake youve made in the X1 much like your vpm boyles law 'oversight' Silent Running, i appreciate you state you are new to this, but you have largely reprinted wienkes spiel about rgbm validation from his website. 1000's of suunto ghekko no-deco dives hardly validate it as a deco model...would you agree? The only 'full' rgbm deco computer should be avoided like the plague, many have been bent with it. FYI suunto only use rgbm on their cardboard boxes - not in their metal ones! How come the peddlers of rgbm/vpm use no-deco dives or tech bimbles to validate/augment their work but when actually used to 'everyday' depths as you say Ross, the divers get bent and you simply blame pilot error? What are we doing wrong oh guru? Mark Mark, This this point you seem to be pretty focused on baiting other people. In your previous post, you specifically say "20M" and now you change your story... ************************************************ *** I used X1 V-Planner Live recently for 60mins at 20metres at 1.1 setpoint (+3)compared with VR3 at 20% conserv and 1.1 setpoint. ********************************************** *** How about contrubuting something versus just bashing everyone... Thanks Mark
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